The submucosally embedded in situ appendix guarantees an ideal continence mechanism in patients with ileocecal urinary reservoirs. To date this modification of the Mainz pouch technique has been performed successfully in 13 patients. The appendicocutaneous stoma was placed at the lower right abdominal quadrant in 12 patients and into the umbilical funnel in 1. Urodynamic investigations of the submucosally embedded appendix showed a maximum closure pressure of more than 80 cm. water in pressure profiles. Only 1 case of stomal stenosis required reoperation.